Referring to FIG. 5, a conventional fan mainly comprises a rotor 1′, a stator 2′, and a housing 3′. The rotor 1′ comprises a hub 10′ with a close end wall and a mouth opposing the close end wall. A number of blades 11′ extend radially outward from the hub 10′. A permanent magnet 104′ is fixedly mounted to the inner surface of the hub 10′ via the mouth after the hub 10′ is formed. However, it is very hard to accurately locate the permanent magnet 104′ in the hub 10′. Furthermore, when any components of the rotor 1′ other than the permanent magnet 104′ is damaged, it is not convenient for tools to enter into the hub 10′ from the mouth of the hub 10′ to detach the permanent magnet 104′ from the hub 10′.
Moreover, in operation of the fan, coils of the stator 2′ are electrified to allow the rotor 1′ to rotate circumambiently around the stator 2′. Therefore, coils of the stator 2′ generate heat continuously. The heat generated by the coil due to electrification of the fan will accumulate within the fan if it is not removed efficiently, which leads to the damage of the fan.
An improved fan that overcomes the above-mentioned disadvantages is desired.